S&G 951

= Sargent and Greenleaf 951 =

The No. 140 is a pin-tumbler padlock made by Master Lock. The No. 140 is a solid body padlock with an inner cylinder that uses four pin stacks and contains spooled security pins.

Principles of operation

 * See also Pin-tumbler (Principles of Operation)

The No. 140 cylinder is a pin-tumbler lock with four pin stacks and one or more spooled security pins in various chambers. Older versions of the lock use one spool pin in the third chamber. The No. 140 can only be opened by rotating the plug clockwise.

Disassembly instructions
The No. 140 cannot be disassembled non-destructively; to disassemble it the lock must be sawed in half. The lock is nonfunctional once disassembled because the padlock body acts as the cylinder for the lock.

Vulnerabilities
The 140s reduced pin-tumbler count and poor manufacturing tolerances allows it to be easily picked by low skill attackers despite having spool pins. It is commonly used in locksport groups and an introductory lock for beginners to learn about defeating security pins. The No. 140 may be vulnerable to one or more of the following:


 * Lockpicking
 * Key bumping
 * Impressioning
 * Bypass
 * Destructive entry